1. Field of the Invention
This invention relates to buoyancy compensators for scuba divers which automatically maintain a predetermined buoyancy.
2. Prior Art
The invention concerns a low-weight device for buoyancy which is intended to be used by divers. The force of buoyancy can be adjusted. Scuba divers usually need a device for buoyancy to compensate their weight while diving to prevent them from sinking or floating to the surface. The buoyancy must be adjustable because the diver's weight changes while diving. Usually a kind of bag is used which is attached to the body and which is filled with different quantities of air. The buoyancy of these diving devices depends on the air volume inside the bag. This volume is not constant, it depends on the water pressure. As the diver sinks the pressure rises with the depth, the volume decreases, the buoyancy decreases too and the diver sinks even faster. This is usually an undesired, sometimes a dangerous effect.
Several improvements have been made to provide a buoyancy compensator with constant, adjustable buoyancy:
East's U.S. Pat. No. 3,820,348 discloses an automatic buoyancy device with a flexible bladder between two rigid plates. The plates, together with a cable mechanism, sense changes of the bladder volume and compensate these changes by allowing the bladder to inflate or deflate. A disadvantage of this device is its rather complicated and bulky construction.
Bohmrich's device (U.S. Pat. No. 4,114,389) consists of a rigid constant volume chamber filled with air. By admitting water into the chamber the buoyancy can be changed. Again this device is bulky and in addition difficult to handle, as several valves must be activated to let the water in or out.